Process for the separation of fluorocarbons using ionic liquids

Abstract

This invention relates to a process for separating 1,1,2,2-tetrafluoroethane or 1,1,1,2-tetrafluoroethane from a mixture comprising both 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane wherein at least one ionic liquid is used to enhance the efficiency of the separation.

1 . A process for separating 1,1,2,2-tetrafluoroethane or 1,1,1,2-tetrafluoroethane from a mixture comprising 1,1,2,2-tetrafluoroethane and 1,1,1,2-tetrafluoroethane, comprising
 (a) contacting the mixture with at least one ionic liquid in which 1,1,1,2-tetrafluoroethane is soluble to a greater extent than 1,1,2,2-tetrafluoroethane and separating 1,1,2,2-tetrafluoroethane from the mixture; or   (b) contacting the mixture with at least one ionic liquid in which 1,1,2,2-tetrafluoroethane is soluble to a greater extent than 1,1,1,2-tetrafluoroethane and separating 1,1,1,2-tetrafluoroethane from the mixture;   wherein an ionic liquid comprises a fluorinated cation, or a fluorinated anion, or both a fluorinated cation and a fluorinated anion.   
     
     
         2 . A process according to  claim 1  wherein 1,1,1,2-tetrafluoroethane is soluble in an ionic liquid to a greater extent than 1,1,2,2-tetrafluoroethane. 
     
     
         3 . A process according to  claim 1  wherein 1,1,2,2-tetrafluoroethane is soluble in an ionic liquid to a greater extent than 1,1,1,2-tetrafluoroethane. 
     
     
         4 . A process according to  claim 1  wherein an ionic liquid comprises a cation selected from the group consisting of the following eleven cations: 
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are independently selected from the group consisting of:
 (i) H; 
 (ii) halogen; 
 (iii) —CH 3 , —C 2 H 5 , or C 3  to C 25  straight-chain, branched or cyclic alkane or alkene, optionally substituted with at least one member selected from the group consisting of Cl, Br, F, I, OH, NH 2  and SH; 
 (iv) —CH 3 , —C 2 H 5 , or C 3  to C 25  straight-chain, branched or cyclic alkane or alkene comprising one to three heteroatoms selected from the group consisting of O, N, Si and S, and optionally substituted with at least one member selected from the group consisting of Cl, Br, F, I, OH, NH 2  and SH; 
 (v) C 6  to C 20  unsubstituted aryl, or C 3  to C 25  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and 
 (vi) C 6  to C 25  substituted aryl, or C 3  to C 25  substituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and wherein said substituted aryl or substituted heteroaryl has one to three substituents independently selected from the group consisting of:
 (1) —CH 3 , —C 2 H 5 , or C 3  to C 25  straight-chain, branched or cyclic alkane or alkene, optionally substituted with at least one member selected from the group consisting of Cl, Br, F I, OH, NH 2  and SH, 
 (2) OH, 
 (3) NH 2 , and 
 (4) SH; 
 
 
       R 7 , R 8 , R 9  and R 10  are independently selected from the group consisting of:
 (vii) —CH 3 , —C 2 H 5 , or C 3  to C 25  straight-chain, branched or cyclic alkane or alkene, optionally substituted with at least one member selected from the group consisting of Cl, Br, F, I, OH, NH 2  and SH; 
 (viii) —CH 3 , —C 2 H 5 , or C 3  to C 25  straight-chain, branched or cyclic alkane or alkene comprising one to three heteroatoms selected from the group consisting of O, N, Si and S, and optionally substituted with at least one member selected from the group consisting of Cl, Br, F, I, OH, NH 2  and SH; 
 (ix) C 6  to C 25  unsubstituted aryl, or C 3  to C 25  unsubstituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and 
 (x) C 6  to C 25  substituted aryl, or C 3  to C 25  substituted heteroaryl having one to three heteroatoms independently selected from the group consisting of O, N, Si and S; and wherein said substituted aryl or substituted heteroaryl has one to three substituents independently selected from the group consisting of:
 (1) —CH 3 , —C 2 H 5 , or C 3  to C 25  straight-chain, branched or cyclic alkane or alkene, optionally substituted with at least one member selected from the group consisting of Cl, Br, F, I, OH, NH 2  and SH, 
 (2) OH, 
 (3) NH 2 , and 
 (4) SH; and 
 
 
       wherein, optionally, at least two of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9  and R 10  together form a cyclic or bicyclic alkanyl or alkenyl group. 
     
     
         5 . A process according to  claim 4  wherein at least one of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10  comprises F—. 
     
     
         6 . A process according to  claim 1  wherein an ionic liquid comprises an anion selected from the group consisting of [CH 3 CO 2 ] − , [HSO 4 ] − , [CH 3 OSO 3 ] − , [C 2 H 5 OSO 3 ] − , [AlCl 4 ] − , [CO 3 ] 2− , [HCO 3 ] − , [NO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , [PO 4 ] 3− , [HPO 4 ] 2− , [H 2 PO 4 ] − , [HSO 3 ] − , [CuCl 2 ] − , Cl − , Br − , I − , SCN − , and any fluorinated anion. 
     
     
         7 . A process according to  claim 1  wherein an ionic liquid comprises an anion selected from the group consisting of [BF 4 ] − , [BF 3 CF 3 ] − , [BF 3 C 2 F 5 ] − , [PF 6 ] − , [PF 3 (C 2 F 5 ) 3 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , [CF 3 CO 2 ] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , [(CF 3 CFHCF 2 SO 2 ) 2 N] − , and F − . 
     
     
         8 . A process according to  claim 1  wherein an ionic liquid comprises a cation selected from the group consisting of imidazolium and pyridinium ions, and an anion selected from the group consisting of [BF 4 ] − , [BF 3 CF 3 ] − , [BF 3 C 2 F 5 ] − , [PF 6 ] − , [PF 3 (C 2 F 5 ) 3 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , [CF 3 CO 2 ] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , [(CF 3 CFHCF 2 SO 2 ) 2 N] −  and [CH 3 OSO 3 ] − . 
     
     
         9 . A process according to  claim 1  wherein an ionic liquid comprises a 1-butyl-3-methylimidazolium cation, and an anion selected from the group consisting of [BF 4 ] − , [BF 3 CF 3 ] − , [BF 3 C 2 F 5 ] − , [PF 6 ] − , [PF 3 (C 2 F 5 ) 3 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , [CF 3 CO 2 ] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , [(CF 3 CFHCF 2 SO 2 ) 2 N] − . 
     
     
         10 . A process according to  claim 1  wherein an ionic liquid comprises a 1-ethyl-3-methylimidazolium cation, and an anion selected from the group consisting of [BF 4 ] − , [BF 3 CF 3 ] − , [BF 3 C 2 F 5 ] − , [PF 6 ] − , [PF 3 (C 2 F 5 ) 3 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , and [CF 3 CO 2 ] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , and [(CF 3 CFHCF 2 SO 2 ) 2 N] − . 
     
     
         11 . A process according to  claim 1  wherein an ionic liquid comprises a 1-ethyl-3-methylimidazolium cation, and an anion selected from the group consisting of [(CF 3 CF 2 SO 2 ) 2 N] − , [PF 6 ] − , and [HCF 2 CF 2 SO 3 ] − . 
     
     
         12 . A process according to  claim 1  wherein an ionic liquid comprises a 1,3-dimethylimidazolium cation, and an anion selected from the group consisting of [BF 4 ] − , [BF 3 CF 3 ] − , [BF 3 C 2 F 5 ] − , [PF 6 ] − , [PF 3 (C 2 F 5 ) 3 ] − , [SbF 6 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [(CF 3 CF 2 SO 2 ) 2 N] − , [(CF 3 SO 2 ) 3 C] − , and [CF 3 CO 2 ] − , [CF 3 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CFHOCF 2 CF 2 SO 3 ] − , [CF 2 HCF 2 OCF 2 CF 2 SO 3 ] − , [CF 2 ICF 2 OCF 2 CF 2 SO 3 ] − , [CF 3 CF 2 OCF 2 CF 2 SO 3 ] − , [(CF 2 HCF 2 SO 2 ) 2 N] − , and [(CF 3 CFHCF 2 SO 2 ) 2 N] − . 
     
     
         13 . A process according to  claim 1  wherein an ionic liquid comprises a 3-methyl-1propylpyridinium cation, and a [(CF 3 SO 2 ) 2 N] −  anion. 
     
     
         14 . A process according to  claim 1  wherein an ionic liquid comprises a 1-hexyl-3-methylimidazolium cation, and a [PF 3 (C 2 F 5 ) 3 ] −  anion. 
     
     
         15 . A process according to  claim 1  which is performed in a distillation column. 
     
     
         16 . A process according to  claim 15  wherein an ionic liquid is fed to the column as an extractant and contacts the mixture in the column. 
     
     
         17 . A process according to  claim 15  wherein 1,1,2,2-tetrafluoroethane exits the top of the column as a vapor. 
     
     
         18 . A process according to  claim 15  wherein 1,1,1,2-tetrafluoroethane exits the top of the column as a vapor. 
     
     
         19 . A process according to  claim 15  wherein the ratio of the moles of ionic liquid fed to the column to the moles of mixture to be separated fed to the column is in the range of from about 0.1 to about 25. 
     
     
         20 . A process according to  claim 15  wherein an ionic liquid is recovered from the column bottoms and is recycled to the column.